1. Field of the Invention
The present invention relates to a method of and apparatus for welding metallic materials of predetermined sizes in a continuous linear state as a preceding step for cutting into desired lengths or bending rod-like metallic material such as metal bars or rods, metal pipes, metal plates or the like.
2. Description of the Prior Art
In general, there are two types of material for the bar steel for reinforcement of concrete (hereinafter, the metallic material will be described as reinforcement steel for concrete): namely, a coiled material and a linear material cut into a predetermined size. The reinforcement steel bar is cut and processed into various sizes and shapes before it is placed in the concrete. When the material is a coiled one, the material is cut into a predetermined length after straightening into a linear state by a straightening machine. In this case, therefore, it is necessary to use a specific straightening machine, although the generation of waste material is avoided advantageously. In addition, the straightening machine is required to have a large and tough construction when the diameter of the material is 19 mm or greater. Also, in such a case, a large power is required for the straighening and the fine projections on the reinforcement steel bar are collapsed to spoil the reinforcement performance inherently required for the reinforcement steel bar. Therefore, the coiled material is not used when the diameter of the bar exceeds 19 mm. Thus, when the diameter of the reinforcement steel bar exceeds 19 mm, it is necessary to use linear material of predetermined size, typically 5 to 10 meters. Since the cutting length varies largely depending on the demand, residual materials or waste is inevitably produced. The amount of waste material is significantly large.
In order to avoid this waste of material, it is considered to weld the materials of predetermined sizes into a continuous linear state by various methods such as flush welding, pressure welding using high-frequency heating or pressure welding by means of gas. The flush welding and high-frequency welding, however, require a specific electric power source, while the pressure welding by gas takes an impractically long working time. These welding methods, therefore, cannot be successfully used when the production amount is large as in the case of reinforcement bar, in both aspects of economy and efficiency.